US2693550A - Television receiver - Google Patents

Television receiver Download PDF

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Publication number
US2693550A
US2693550A US288924A US28892452A US2693550A US 2693550 A US2693550 A US 2693550A US 288924 A US288924 A US 288924A US 28892452 A US28892452 A US 28892452A US 2693550 A US2693550 A US 2693550A
Authority
US
United States
Prior art keywords
potentiometer
switch
tube
television receiver
brilliance
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US288924A
Other languages
English (en)
Inventor
Doherty Stephen Norman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hartford National Bank and Trust Co
Original Assignee
Hartford National Bank and Trust Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hartford National Bank and Trust Co filed Critical Hartford National Bank and Trust Co
Application granted granted Critical
Publication of US2693550A publication Critical patent/US2693550A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N3/00—Scanning details of television systems; Combination thereof with generation of supply voltages
    • H04N3/10—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical
    • H04N3/16—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by deflecting electron beam in cathode-ray tube, e.g. scanning corrections
    • H04N3/20—Prevention of damage to cathode-ray tubes in the event of failure of scanning

Definitions

  • the invention relates to television receivers and has particular reference to receivers employing permanent magnet focussing of the cathode ray tube electron beam.
  • This eiiect is most marked if the set is switched off with the brillance control at its minimum position or when there is no modulation and consequently no electron beam.
  • the object of the invention is to reduce the possibility of such damage under these conditions.
  • a television receiver employing a cathode ray tube having permanent magnet focussing is characterised by the provision of a combined brilliance control potentiometer and main on-off switch, the potentiometer and switch being so arranged and/or connected that the switch can only be operated with the control at its maximum brilliance position.
  • the cathode In a television receiver employing a cathode ray tube with permanent magnet focussing and cathode modulation the cathode is maintained during operation at a standing positive potential (of the order of 150 volts) with respect to earth by reason of its connections to the sides output valve.
  • the C. R. tube control grid In order to control the brilliance the C. R. tube control grid is adjusted to a slightly lower positive potential by a potentiometer forming part of a 2,693,550 Patented Nov. 2, 1954 2 potential dividing network connected between the positive pole of the normal H. T. line (for example of 250 volts) and earth.
  • a fixed resistor 1 of suitable value is connected between the H. T. positive line and one end of the potentiometer 2 and another fixed resistor 3 is connected between the other end of the potentiometer and earth, the slider 4 being connected to the control grid 5 of the C. R. tube.
  • the main on-ofr" switch 6 of the receiver is mechanically combined with the brilliance potentiometer as indicated by the dotted line, instead of the sound volume control as is more usual, so as to be operated by the movement of the slider at one end of its travel.
  • the potentiometer is so connected that when the switch is operated the slider is at the full brilliance end of its travel, this being the end of the resistance track connected to the H. T. line through the fixed resistor 1.
  • a permanent focussing magnet which may be of a type well-known in the art, is shown schematically at 8.
  • the line and frame deflecting potentials do not collapse instantaneously since the cathodes of the time base valves remain hot after the heaters are switched off and the main H. T. smoothing capacitors continue for a short time to deliver current.
  • the grid-cathode potential of the C. R. tube by the arrangement above described, is such that there is an electron beam even in the absence of modulation of sufficient magnitude to discharge the E. H. T. capacitor before the line and frame deflecting potentials have collapsed.
  • the potentiometer With combined potentiometer and switch arrangements of the usual kind the potentiometer will be operated in an anticlockwise direction for increase of brilliance which is the opposite rotation to that usually employed. It desired, this hand of rotation may be reversed by arranging the switch to be operated to its on position by anticlockwise rotation of the control spindle. In this case the operating regime may be to switch on the set and continue to rotate the potentiometer to the other extreme of its travel then increasing the brillance by normal clockwise rotation to the desired position. To switch oti the set, the control may be rapidly advanced to the full brilliance position until the switch is operated.
  • control grid stopper resistor '7 may be included between the potentiometer slider 4 and the control grid 5 of the C. R. tube to limit the flow of grid current while permitting the grid to be held at a potential such that the electron beam from the C. R. tube cathode can form a discharge path of sufficient magnitude for the charge held by the E. H. T. capacitor to be dissipated in the time available.
  • a cathode-ray tube provided with permanent magnet focussing for displaying the incoming images, means including a potentiometer coupled to said tube to control the brilliance of said images, a power supply for said receiver including a main onoff switch for connecting said supply to an energizing source, and means mechanically linking said switch to said potentiometer to effect a switching-01f operation only when said potentiometer is adjusted to a position producing maximum brilliance.

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Details Of Television Scanning (AREA)
US288924A 1951-05-22 1952-05-20 Television receiver Expired - Lifetime US2693550A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB301974X 1951-05-22

Publications (1)

Publication Number Publication Date
US2693550A true US2693550A (en) 1954-11-02

Family

ID=10303812

Family Applications (1)

Application Number Title Priority Date Filing Date
US288924A Expired - Lifetime US2693550A (en) 1951-05-22 1952-05-20 Television receiver

Country Status (7)

Country Link
US (1) US2693550A (US07166745-20070123-C00016.png)
BE (1) BE511562A (US07166745-20070123-C00016.png)
CH (1) CH301974A (US07166745-20070123-C00016.png)
DE (1) DE915943C (US07166745-20070123-C00016.png)
FR (1) FR1102925A (US07166745-20070123-C00016.png)
GB (1) GB702166A (US07166745-20070123-C00016.png)
NL (1) NL82719C (US07166745-20070123-C00016.png)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3015751A (en) * 1958-03-07 1962-01-02 Philips Corp Circuit for adjusting the background brightness in television reproducing device

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3015751A (en) * 1958-03-07 1962-01-02 Philips Corp Circuit for adjusting the background brightness in television reproducing device

Also Published As

Publication number Publication date
BE511562A (US07166745-20070123-C00016.png)
FR1102925A (fr) 1955-10-27
DE915943C (de) 1954-08-02
GB702166A (en) 1954-01-13
NL82719C (US07166745-20070123-C00016.png)
CH301974A (de) 1954-09-30

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